package udp;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;


public class UdpEchoServer {
    private DatagramSocket socket = null;

    public UdpEchoServer(int port) throws SocketException {
        socket = new DatagramSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务器启动!");
        while(true) {
            //1.读取请求并解析
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096],4096);
            socket.receive(requestPacket);
            String request = new String(requestPacket.getData(),0,requestPacket.getLength());
            //2.根据请求处理
            String response = process(request);
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(),0, response.getBytes().length,
                    requestPacket.getSocketAddress());
            //3.返回
            socket.send(responsePacket);
            //4.打印日志
            System.out.printf("[%s:%d] res: %s resp: %s\n",requestPacket.getAddress(),requestPacket.getPort(),
                    request,response);
        }
    }

    public String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer server = new UdpEchoServer(9090);
        server.start();
    }
}
